Telemeter.



0 EPPENSTEIN. TELEMETEE. .AlfBI-ICATIQN FILED JAIL-,7, 1911.

1 ,016 5325, v Patented Feb. 6, 1912.

COLUMBIA PLANOGRAPH Co., WASHINGTON, D. c.

UNITED STATES PATENT OFFICE.

OTTO EPPENSTEIN, OF JENA, GERMANY, ASSIGNOR TO THE FIRM 0F CARL ZEISS, OF J ENA, GERMANY.

TELEMETER.

Specification of Letters Patent.

Application filed January 7, 1911.

Patented Feb. 6, 1912.

Serial No. 601,480.

T 0 all whom it may concern:

Be it known that I, OTTO ErrENsTnIN, a citizen of the German Empire, residing at Garl-Zeiss strasse, Jena, in the Grand Duchy of Saxe-Weimar, Germany, have invented a new and useful Telemeter, of which the following is a specification.

The invention relates to coincidence telemeters, in which the one image is inverted in the direction perpendicular to the base line and is further so arranged that it is inclosed by the other image with boundary lines parallel to the base line, no matter whether these two boundary lines extend as far as the margin of the field of View or whether the inverted image is entirely surrounded by the erect one. Such telemeters have always been constructed with horizontal base line, consequently also with horizontal boundary lines between the inclosed and the inclosing image, the image pair then having such a position as regards height,- that its locus of coincidence, i. 6. in the type of telemeter under consideration that straight line, parallel to the base line, in which corresponding points of both images lie and are brought into coincidence in pairs 1 when finding a range, coincides with the lower boundary line. This well-known disposition answers its purpose in the case, where the object, the distance of which is to be measured, shows in its upper part an approximately vertical line or a point, but not in the certainly less frequent case, where only in the lower part of the object there is such a line or a point.

In order that the telemeter may be no less efiicient in the last named case, provision is made according to the present invention for making the upper boundary line alternately with the lower one the locus of coincidence, by lowering or raising the locus of coincidence by the relative distance apart of the two boundary lines through the lowering or raising of the image pair or one of the two images. The changing device which serves for this purpose is appropriately fitted with marks or stops, which permit of the changing being carried out without a simultaneous observation of the images.

Devices for altering the position-of the image pair or of one of the images as to height are already in use with coincidence telemeters of the type under consideration, namely for the purpose of correcting the locus of coincidence, 2'. c. for removing any small deviation of the same from the lower boundary line. The range of motion of such an arrangement is correspondingly of a less order of magnitude than that which is requisite for the new purpose. On the other hand every such correcting device can, as regards its general arrangement, also be used as a changing device, whether its optical part be of an additional character (6. g. a shiftable refracting prism, a rotatable plano-parallel plate, etc.,) or belong to the optical system of the telemeter proper. It

goes without saying, that a changing device belonging to only one half of the telemeter, therefore influencing only the position as to height of one of the images, must raise and lower this image by double the relative distance apart of the two boundary lines, as the locus of coincidence follows the movement of the image only a half of the way.

In the annexed drawing: Figure 1 represents the image field of a telemeter constructed according to the invention. Fig. 2 represents the same image field, the telemeter being set for another object. Fig. 3 represents the same image field, the telemeter being set for another part of the sec ond object. Fig. 4 represents the same image field, the telemeter being set for the :same part of the second object as in Fig. 3, but the locus of coincidence being another one. Fig. 5 is a plan view, partly in section, of a telemeter constructed according to the invention. Fig. 6 is an elevation of the same instrument, the ocular being omited.

The first four figures of the drawing are intended to explain the general idea of the invention. In the field of view divided by the boundary lines a; and b, there appear two objects, the erect images of which are marked cand d and the inverted images of which.c and d". As far as an image is visible, the erect one without, the inverted one within the pair of boundary lines, it is shown in full lines. For the sake of clearas d (P by means of its top edge, when the position of coincidence of the two image points falling in the line a can obviously be observed only inaccurately. In Fig. 3 is shown another attempt, namely to utilize I the vertical lines at the lower end of the object d cZ when determining the distance.

" Such a measurement would certainly have the requisite accuracy, but offers certain practical ditficulties, as the main part of the object is invisible. Now by shifting the changing device let the locus of coincidence be removed from the lower boundary line a into the upper one I The alteration in the position of the images, caused by this re- .moval, is different, according as the changing device has acted on the image pair (raising it by the relative distance apart of a and b) or on only one of the images (raising it by double the relative distance apart of a and b). In the second case this alteration further depends on whether the erect or the inverted image has been raised. Given that previously, while a was the locus of coincidence, the position of the images was as in Fig. 3, the removal of the locus of coincidence into the boundary line b by raising the image pair leads directly to the position of the images in Fig. 4. If the same removal was brought about by raising one of the images, it is also necessary, in order to arrive at the position of the images in Fig. 4, to reset the instrument as regards elevation, always by the angle which corresponds to thedistance between a andfb, upward, when. the changing device has raised the erect image, downward, when it has raised the inverted one. As is seen from Fig. 4, the-measurement may now be carried out 5 by means of the vertical lines at the lower end of d d, while the main part of this object is visible.

In the simple constructional form of the telemeter, shown in Figs. 5. and 6, the ocular prism system consists of three superimposed, simple reflecting. prisms e f g, of which the middle one f coacting with the objective prism h and the objective lens 13 at the left end of the instrument conveys the inverted image to the occular lens system is Z, while the upper prism e and the lower one g with the right-hand'objective system at n form .the erect image,

A shiftable retracting prism 0, the principal section of which is horizontal, forms the optical part of the measuring device. A second prism 22 of this type with vertical principal section represents the optical part of the changing device. In the example chosen this device is built into the left half of the instrument and therefore influences, according to the above, the position as to height of the inverted image. The mounting g of the prism 72 is fitted with a pin 9 projecting through the slot 1' of the casing to the outside and may be shifted by means of the said pin in a guide .9 between the stops 8 s of the same. As the refracting edge of the prism p lies at the top, the end position of the changing device as shown corresponds to the lowest position of the inverted image, in which the locus of coincidence coincides with the lower boundary line. In order to be able to use the same device for the correction of the locus of coincidence, the guide 8 is itself guided by means of a guide-bracket t and forms the nut of the adjusting screw it, which latter is journaled in a fixed bearing.

I claim:

1. The combination, with a coincidence telemeter of the type presenting one image erect and the other image inverted. in the direction perpendicular to the base line and having the inverted image inclosed by the erect image and separated from it by boundary lines parallel to the base line, of means for moving the locus of coincidence from one boundary line to the other by varying the position of the two images relatively to each other in the direction perpendicular to the base line, this means differing in the range of motion from such as are used for correct ing the locus of coincidence.

2. The combination, with a coincidence telemeter of the type presenting one image erect and the other image inverted in the direction perpendicular to the base line and having the inverted image inclosed by the erect image and separated from it by boundary lines parallel to the base line, of means for moving the locus of coincidence from one boundary line to the other by varying the position of the two images relatively to each other in the direction perpendicular to the base line, this means differing in the range of motion from such as are used for correcting the locus of coincidence and comprising two stops limiting the movement of the said locus to the distance between the two boundary lines.

3. The combination, with a coincidence telemeter of the type presenting one image erect and the other image inverted in the direction perpendicular to the base line and having the inverted image inclosed by the erect image and separated from it by boundary lines parallel to the base line, of means for moving the locus of coincidence from one boundary line to the other by varying the position of the two images relatively to two boundary lines and adopted to be adeach other in the direction perpendicular to justed conjointly.

the base line this means differing in the OTTO EPPENSTEIN range of motlon from such as are used for 5 correcting the locus of coincidence and com- Witnesses:

prising two stops limiting the movement of PAUL KRt'ionR, the said locus to the distance between the RICHARD HAHN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. C. 

